Electric discharge device structure



Dec. 2, 1958 w. E. POLSTER ELECTRIC DISCHARGE DEVICE STRUCTURE Filed Nov. 2i, 195s FIG.|.

FIG.3.

INVENTORI WILLIAM E. POLSTER,

TORNY.

HIS

I VI B States ELECTRIC DliSfIl-TARGE DEVICE STRUCTURE William E. Polster, Evanston, Ind, assignor to General Electric Company, a corporation of New York My invention relates to electric discharge devices and pertains more particularly to a new and improved electric discharge device structure including a new and improved electrode mounting arrangement.

Some electric discharge devices, such as high voltage diodes, include an envelope, a tubular anode in the envelope and a filamentary cathode supported in the envelope and disposed in the anode. Several difficulties are generally encountered in this type of structure. For example, due to the relatively high difference in potential generally existing between the filamentary cathode and anode an electric field is set up between these elements which tends to cause the filamentary cathode to flex or how outwardly of its desired normal position. Repeated flexing tends to cause the cathode to pull out and be disconnected from its mounts and to be fractured as a result of fatigue failure. Additionally, the high potential difference between the electrodes has been found often to result in arcing therebetween, especially where the bowing moves the cathode closer to the anode, which arcing has a tendency to melt and thus fracture the cathode. Either cathode pull-out or fracture of the cathode will render the device inoperative.

Accordingly, a primary object of my invention is to provide a new and improved electric discharge device structure.

Another object of my invention is to provide a new and improved support structure for a filamentary cathode.

Another object of my invention is to provide an electric discharge device of improved electrode stability under relatively high voltage operating conditions.

Another object of my invention is to provide a new and improved support structure for a filamentary cathode that will effectively minimize attraction between the oathode and an associated anode.

Another object of my invention is to provide a new and improved filamentary cathode support structure adapted for affording a more uniform emission pattern between the cathode and associated anode.

Another object of my invention is to provide a new and improved filamentary cathode support structure adapted for effectively cancelling electrical forces tending to deflect the cathode with respect to another associated electrode without substantially increasing the internal resistance between the electrodes.

Still another object of my invention is to provide a new and improved electric discharge device including means adapted for minimizing any tendency toward arcing between relatively high and low potential electrodes therein and without substantially increasing the internal resistance of the device.

Further objects and advantages of my invention will become apparent as the following description proceeds and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming part of this specification.

In carrying out the objects of my invention, 1 provide ice an electric discharge device including an envelope having a hollow electrode supported therein. Extending coaxially in the hollow electrode is a filamentary electrode supported between longitudinally spaced end portions of a plurality of spaced support rods extending into the hollow electrode. Supported on one of the support rods is a refractory metal rod which extends substantially parallel to the filamentary electrode and is relatively substantially thinner than the filamentary electrode.

For a better understanding of my invention, reference may be had to the accompanying drawing wherein:

Fig. 1 is an enlarged partially broken away elevational View of an electric discharge device constructed in accordance with an embodiment of my invention;

Fig. 2 is an enlarged fragmentary partially broken away view further illustrating the embodiment of Fig. l; and

Fig. 3 is an enlarged fragmentary view of a modified form of my invention.

Referring to Fig. l, I have shown my invention embodied in an electric discharge device of the type generally referred to in the industry as a high voltage rectifier or diode. From the outset it is to be understood that my invention is not limited in application to this particular type of device, but is equally applicable to other devices wherein the undesirable effects of filament flexing and arcing are encountered.

The device illustrated in Fig. 1 comprises a substantially insulative envelope 1 provided at one extremity with a conductive end-cap 2. The end-cap 2 is suitably sealed in the envelope and makes electrical connection with and supports in the envelope a hollow anode 3 which may be tubular or cylindrical. Secured on the end of the envelope opposite the end-cap 2 is an insulative base 4 carrying a plurality of conductive pins or prongs 5. The prongs 5, in the usual manner, provide electrical connections to a plurality of leads 6 which have portions extending in a suitably sealed manner through the lower end of the envelope 1.

Suitably supported on a plurality of leads 6 in the envelope is an inverted cup-shaped shield 7. Also suitably supported by the leads 6 and an insulative member (not shown) in the bottom of the shield '7 isa spaced pair of elongated conductive filament connectors or support rods 10 and 11. The rods ill and 111 are preferably parallel and include portions extending into the tubular anode 3 in spaced relation to and on opposite sides of the longitudinal axis of the anode. The rod ltd is longer than the rod Jill and thus is adapted for extending farther into the anode in the manner illustrated. Additionally, the rods ill and 11 are formed to include upper or inner-end portions 12 and 13, respectively, which extend transverse the longitudinal axis of the anode.

Thus, the upper or inner-end portion 12 of the rod lltl and the upper or inner-end portion 13 of the rod 11 are spaced longitudinally along the axis of the anode 3. Additionally, and as seen in Fig. 2 also, the end portions 12 and 113 are flattened at least on one side. This facilitates securing to these end portions, as by spot welding, the extremities of a filamentary cathode or filament 15 which preferably is in the form of a coil or helix. As

will be seen in Figs. 1 and 2, the filamentary cathode or filament 15 extends coaxial with the longitudinal axis of the anode 3. This is a preferred disposition of the filament inasmuch as all portions thereof are thus arranged equidistant and as physically remote as possible from the surrounding walls of the anode which affords a substantially uniform emission pattern and tends to minimize arcing between the filament and anode.

Now, in normal operation of the described discharge device relatively high potential differences exist between the cathode and anode resulting in attractive forces tending to cause the filament 15 to flex or bow out of its desired coaxial position toward the anode. If this flexing or bowing is permitted to take place it tends to cause the ends of the filament 15 to be pulled off the end portions 12 and 13 of the support rods or to fracture due to fatigue failure resulting from repeated flexing. Additionally, movement of the filament 15 toward the anode 3 increases susceptibility of the structure to arcing between the electrodes under relatively high voltage excitation. In order to avoid the just-described undesirable effects I have provided an elongated refractory metal wire shield or rod-like element which is suitably secured, as by spot-welding, to the surface of the support rod 11. The element 16 is preferably formed of tungsten and extends substantially parallel to the axis of the filament 15 for the full length at least of the coiled or helical portion thereof.

Additionally, and as perhaps best seen in Fig. 2, the refractory rod'16 is disposed substantially diametrically opposite the support rod and is relatively substantially thinner than the filamentary electrode 15. Thus, the rod 16 provides for shielding of the filamentary electrode or for neutralizing attractive forces between the filamentary cathode and the anode, thereby to minimize flexing or bowing of the cathode. Furthermore, the relative thinness of the rod 16 enables it to provide the required shielding without appreciably increasing the tube-drop or internal resistance between the cathode and anode.

Still further, the small dimension of the rod 16 results in a concentrated field at the end portion thereof with the result that any arcing tending to occur between the cathode and anode instead occurs between the anode and the rod 16. 7 Thus, fracture or any other damage to the filamentary cathode, as would be eflected by arcing, is avoided. The rod 16 is formed of tungsten or any other suitable refractory material in order to enable it to withstand the heat of arcing. Additionally, the rod 16 is adapted for being self-supporting regardless of its small cross-sectional dimension and for withstanding and remaining upright after a drop test or any other shock conditions that may be ordinarily encountered in tube life.

In Fig. 3 is illustrated a modified form of my invention wherein spaced parallel support rods or filament connectors 21 and 2.2 are provided which extend into the anode 3 preferably along axes one of which is substantially coaxial with the longitudinal axis of the anode. In this construction the rod 21 is the longer and the upper extremity thereof comprises a bent portion 23 extending transverse the longitudinal axis of the anode. Thus, the portion 23 and the upper end of the rod 22 are disposed in spaced relation along the longitudinal axis of the anode and are adapted for having secured thereto, as by spotwelding, the corresponding ends of a coiled or helical filamentary cathode 24 in the manner illustrated in Fig. 3. As seen, the upper ends of the rods may be flattened to facilitate securing the filament in the desired position. In this manner, the filamentary cathode 24 is disposed coaxial with the anode for the desirable purposes abovedescribed. Additionally, in the presently-described modification I have formed the upper end of the rod 22 to include a portion 26 which extends radially for a substantial length. Secured to the same side of the portion 26 as the lower end of the filament 24, as by spot-welding, is a refractory metal Wire shield or rod-like element 27.

.Thus, the shield is supported diametrically opposite the 4 of my invention I do not desire my invention to be limited to the particular forms shown and described, and I intend by the appended claims to cover all modifications within the spirit and scope of my invention.

What! claim as new and desire to secure by Letters Patent of the United States is:

1. An electric discharge device comprising an envelope, a hollow electrode in said envelope, a filamentary electrode in said envelope and disposed in said hollow electrode, and a high-refractory metal element supported in said hollow electrode and extending on only one side of said filamentary electrode in substantially parallel spaced relation to and for approximately the full length of said filamentary electrode.

2. An electric discharge device comprising, an envelope, a tubular electrode in said envelope, an elongated filamentary electrode in said envelope supported coaxially in said tubular electrode, and relatively thin refractory metal straight rod-like element supported in said tubular electrode and extending in substantially parallel spaced relation to said filamentary electrode for approximately the full length of said filamentary electrode and being electrically connected at one end to said filamentary electrode.

3. An electric discharge device comprising, an envelope, a tubular electrode in said envelope, a filamentary electrode in said envelope supported coaxially in said tubular electrode, and a relatively thin tungsten rod-like element supported in said tubular electrode and having a free end extending in substantially parallel spaced relation to said filamentary electrode for substantially the full length thereof. the opposite end of said element being electrically connected to said filamentary electrode.

4. An electric discharge device comprising an envelope, a tubular anode in said envelope, a pair of spaced support rods of unequal lengths in said envelope and extending into said anode, a filamentary cathode supported in said anode between the inner-end portions of said support rods, and a refractory metal rod-like element mounted at one end on one of said support rods and including a free opposite end extending in substantially parallel spaced relation to said cathode for substantially the full length of said cathode.

5. An electric discharge device comprising an envelope, a tubular electrode in said envelope, a pair of spaced substantially parallel support rods in said envelope extending into said anode and being of unequal lengths, a filamentary cathode supported in said cathode by the inner-end portions of said support rods, and a relatively thin straight tungsten rod-like element mounted at one end the shorter of said support rods and extending in substantially parallel spaced relation to said cathode for substantially the full length of said cathode on the side thereof opposite the longer of said support rods.

6. An electric discharge device comprising an envelope, a tubular anode in said envelope, a pair of spaced substantially parallel support rods in said envelope extending into said anode and being of unequal lengths, at least one of said support rods being coaxial with said anode and the other including an end portion extending transverse the longitudinal axis of said anode, a filamentary cathode coaxially supported in said anode between the inner-end portions of said support rods and a refractory metal rodlike element mounted at one end on one of said support rods and including a wholly straight free opposite end extending in substantially parallel spaced relation to said cathode.

7. An electric discharge device comprising an envelope, a tubular anode in said envelope, a pair of spaced substantially parallel support rods in said envelope extending into said anode and being of unequal lengths, at least one of said support rods being coaxial with said anode and the other including an end portion extending transverse the longitudinal axis of said anode, a filamentary cathode coaxially supported in said anode on the inner-end portions of said support rods, and a relatively thin tungsten rodlike element mounted at one end on the shorter rod and having a free opposite end extending in substantially parallel spaced relation to said cathode for substantially the full length of said cathode on the side thereof opposite the longer of said support rods.

8. An electric discharge device comprising an envelope, a tubular electrode in said envelope, a pair of spaced substantially parallel support rods of unequal lengths in said envelope, said support rods extending into said anode in parallel relation to and on opposite sides of the longitudinal axis of said anode, said support rods including inner-end portions extending transverse said longitudinal axis of said anode, a filamentary cathode coaxially supported in said anode between said inner end portions of said support rod, and a refractory metal rodlike element mounted at one end on one of said support rods and including a straight free end extending in substantially parallel spaced relation to said cathode.

9. An electric discharge device comprising an envelope, a tubular anode in said envelope, a pair of spaced substantially parallel support rods, said support rods extending into said anode in parallel relation to and on opposite sides of the longitudinal axis of said anode, said support rods including inner-end portions extending transverse said longitudinal axis of said anode, a filamentary cathode coaxially supported in said anode between said inner end portions of said support rod and a relatively thin tungsten rod-like element having one end mounted on the shorter of said support rods and having a free end extending in substantially parallel spaced relation to said cathode for substantially the full length thereof on the side thereof opposite the longer of said support rods.

References Cited in the file of this patent UNITED STATES PATENTS 391,596 Edison Oct. 23, 1888 1,886,264 Pohlhausen Nov. 1, 1932 2,108,533 Henry Feb. 15, 1938 2,477,110 Atlee et al July 26, 1949 2,558,603 Atlee June 26, 1951 2,656,479 Brown Oct. 20, 1953 

